def test_insert_before(self):
l = SingleLinkedList([1])
node = l.get_n_th_node(0)
l.insert_before(node, 5)
self._check_list(l, (5, 1))
l.insert_before(node, 4)
self._check_list(l, (5, 4, 1))
l.insert_before(l.get_n_th_node(0), 9)
self._check_list(l, (9, 5, 4, 1))
l.insert_before(l.get_n_th_node(2), 12)
self._check_list(l, (9, 5, 12, 4, 1))
